1. Investigation of foraging habits and prey selectivity by humpback whales using acoustic tags and concurrent fish surveys Briana H. Witteveen 1, Robert J. Foy 1, Kate M. Wynne 1, & Yann Tremblay 2 1 University of Alaska Fairbanks School of Fisheries and Ocean Sciences 2 University of California Santa Cruz Long Marine Laboratory

2. Generalists feeding on euphausiids and pelagic fish species –Many prey species are linked to other consumers Need for reliable species-specific estimates of seasonal abundance, diet composition,and prey consumption Humpback whales - one of many apex predators

4. Tagging animals can determine depth of dive explicitly Acoustic time depth transmitters (ATDTs) allow for continuous dive depth data to be received in real time Utility in combining ATDTs and prey sampling to describe prey selectivity and habits of baleen whales This study reports first efforts to investigate humpback whale foraging habits with ATDTs while concurrently assessing prey availability

5. 3 – 8 August 2004 Effort within ~144 km 2 area 10 miles east of Spruce Island Area selected based on the presence of a large aggregation of humpback whales

6. Suction cup VEMCO ATDT Telonics VHF Crossbow deployment R/V Soundwave

7. Visual coding Dive data analyzed using IKNOS (Y. Tremblay, unpublished software) –outputs 14 parameters Means of parameters were averaged across whales T-tests of parameters

8. Concurrent Prey Sampling Sub-area 1 Sub-area 2 F/V Alaskan Track

9. Hydroacoustics Simrad EK 60 echosounder 38/120 kHz freq. Calibrated 3x per year Hull mounted transducer SonarData Echoview Commercial Nets DanTrawl Bering Billionaire Midwater Trawl 5m Nets V-doors

10. 4 successful attachments ~17 hours total tracking 104 dives Results

12. 3 and 5 labeled as “foraging” –Mean depth = 106.2 m (SD: 93 - 120m) 3 and 5 differentiated by bottom range –Range of depth covered during bottom phase –Indicator of oscillations at depth Horizontal Foraging Vertical Lunge Foraging 3 5

13. Capelin Age-0 Pollock Whale Tracks

14. Distribution of Humpback Foraging Dives Distribution of Capelin/km 2

15. Hydroacoustic Prey Sampling Depth adult pollock, eulachon & euphausiids Depth capelin

16. Summary and Conclusions Fish surveys showed that pollock and capelin were present in significant densities within the study area and should be available as whale forage. Examination of the fish present along the tracks of the tagged whales suggests a preference for capelin as a prey source. Humpback whale foraging dives (types 3 and 5) occurred at an average depth of 106.2 meters and corresponded to the highest numbers of available capelin

17. Summary and Conclusions Cont. Were there simply more capelin available? No quantitative assessment of zooplankton, but backscatter showed them at depths exceeding humpback foraging dives Real-time dive data allow for fine-tuned sampling of prey and improve the ability to describe prey selectivity

18. Future Directions Addition of zooplankton assessment in prey surveys Concurrent tagging on humpbacks and fin whales when co-occurring spatially Tag redesign to increase deployment efficiency and length of attachment

19. Captain and crew of the F/V Alaskan Jordy Thomson, Casey Clark, & Petra Reimann for field assistance Robin Baird, Gregg Schorr, Don Croll, & Kelly Newton Funding provided by NOAA Grant #NA16FX1270 Research conducted under NMFS Scientific Research Permit No. 1049- 1718-00, UAF IACUC #02-38, UAF IACUC #04-21, ADF&G #CF-04-031, and NFMS LOA #2004-06. Acknowledgements